This invention relates to an instrument assembly.
It is often required that an instrument assembly should provide a visual indication of both the current value of a parameter and of the required or set value of the same parameter. The instrument assembly will usually also include the comparison devices, for example electronic circuitry, which serve to provide an input to the apparatus being controlled in accordance with the relationship of the current value of the parameter to the set value. For safety and aesthetic reasons it is desirable that the device should give as clear an indication as possible of the relationship of the current value and the set value at any instant in time and that the instrument assembly itself should be designed and constructed in such a way that there is as little potential obstruction to visibility as possible.
G. B. Patent 1,358,746 describes an instrument assembly in which two separate scales are provided and the two readings are taken at 180.degree. apart.
G. B. Patent 1,380,031 describes an instrument assembly in which the current value indicator element is provided by the combination of a coloured arcuate strip and a slot in a rotating disc both of which are located behind the scale plate which itself has to be provided with an arcuate slot equal in length to the scale length.